Protective device



Sept. 4, 1951 J. w. KALB 2,566,895

PROTECTIVE DEVICE Filed Aug. 25, 1949 Inventor: John W. Kalb JOLJ W Hi5 Attorney.

Patented Sept. 4, 1951 PROTECTIVE DEVICE John W. Kalb, Barberton, Ohio, assignor to General Electric Company, a corporation of New York Application AugusjtZS, 1949, Serial No. 111,907

This invention relates to protective devices and more particularly to lightning arrestors which will aiford reliable protection against transient voltages in either direct or alternating current electric circuits.

The usual arr-ester most generally employed in the industry includes a spark gap and a resistance and can be used for the protection of alternating current circuits only. An excessive transient voltage may cause the gap to spark over and permit a power follow current to be established through the arrester. Because of the alternating'wave form of the applied power voltage, the follow current will pass through zero at the end of the first half cycle of the power frequency so that it may be interrupted by the gap. Such an arrester cannot function when applied to a direct current circuit because the follow current does not pass through zero and therefore cannot be interrupted by the gap. On the other hand, there are other interrupting devices which either move an are at relatively slow speed into a restricted arc slot or chute which is vented at the end toward which the arc moves or'moves the are at relatively high speed through a restricted passage into a larger expansion chamber. However, it has been found that the interrupting ability of all such devices is limited when applied to conventional circuits of higher current capacities. Moreover, all prior art vented devices are objectionable from the point of view of-noise, safety hazard to personnel and danger of striking arcs to other nearby conducting objects.

It is therefore an object of this invention to provide a circuit interrupting device which when applied to circuits of higher current capacities will efiectively interrupt currents of either direct or alternating characteristic.

It is also an object of this invention to provide an interrupting device concerning which the necessity for a resistance element to limit the normal power current is eliminated.

It is a further object of this invention to provide a device which need not be vented to the atmosphere but may be completely enclosed.

It is still a further object of this invention to provide a protective device which will pinch off or snuff out an arc in a relatively small fraction of the time normally taken for power frequencies of alternating current to reach the zero value at the end of the first half cycle.

In accordance with this invention, I provide an arc gap defined by a pair of spaced electrodes adjacent to an arc extinguishing chamber the walls of which are spaced a maximum in the vi- 6 Claims.- (Cl. 315347) '2 cinity of the gap and converge progressively together at points remote therefrom together with means positioned or mounted adjacent the electrodes and chamber providing a magnetic field so that upon establishment of an are between the electrodes the field will elongate and rapidly move the arc to the constricted periphery of the chamber where it will be pinched off or extinguished. 4

The invention will be better understood from the following description when taken in connection with the accompanying drawing and the scope of the invention will be pointed out in the appended claims. In the drawing, Fig. 1 shows a side elevation view of the device and a diagrammatic sketch of a simple circuit to illustrate its operative relationship thereto; Fig. 2 is a plan or top view of the device proper'partly broken away to better illustrate the electrode arrangement therein and the configuration of an arcing cham ber relative thereto; 'Fig. 3 is a sectional view taken on the line 3- -3 of Fig. 2 and Fig. 4 is a sectional view taken on the line 4 -4 of Fig. 2.

Referring now'to' the details'of the various figures of the drawing; a'body of insulating material is provided comprising, V in the particular illustrations shown, a pair of abutting blocks or slabs I0 and I I of insulating material having a cylindrical external configuration. Between the blocks and adjacent the edge or periphery thereof are positioned a pair of spaced electrodes I2 and I3 defining an arc gap therebetween. Electrode I2 is fixed to or mounted on the lower block II! by means of screw I4 of conducting material which also-serves to hold'acircular plate I5 of conducting material'against the lower end surface of block In while electrode I3 and another plate I6 are similarly mounted on block II by conducting screw II. Thus, electrode I2 is electrically connected to plate I5 and electrode I3- is electrically connected to plate I6. The opposing surfaces I8 and I9 of blocks I0 and I I, respectively, are depressed inwardly from the abutting edges thereof so as to define an arcing chamber 20 in communication with the electrodes I2 and I3 and the walls of which have a maximum spac ing adjacent the electrodes and progressively converge-together at points remote from the gap spacing therebetween. In other words, as better illustrated by Fig. 4 the spacing between the walls of arcing chamber 20 becomes progressively more restricted in any and all-directions from the vicinity of the electrodes as the distance inwardly therefrom isincreased until the walls come torfl 0r 'adia en mthe a tti edges of 3 the blocks to form a substantially enclosed arcing chamber.

As part of this invention, means is provided adjacent the blocks to produce a magnetic field which will act upon any are once established between electrodes |2 and I3. For example, a coil or winding 2| is mounted closely adjacent the abutting blocks l0 and H in the manner illustrated by Fig. 1 so that an magnetic field pro duced by the winding will traverse the gap space between the electrodes in a, direction transversely thereto and transverse to the plane of the joint between the blocks l0 and I. 'One end of the Winding is electrically connected to one of the conducting plates such as Hi, asshown in Figure 1 while the other plate I 5 is represented as being connected to ground. The other end of the-coil winding is represented as being connected to a line circuit 22 having either direct or alternating current characteristics. Thus the coil is connected through plate i6 and screw electrically in series with one of the electrodes i3 or with the gap between the electrodes.

Passage of surge currents with steep wave fronts through the inductance of coil 2| would result in a high voltage drop acrossthe coil permitting line 22 to rise to a high potential above ground. Since it is an object of this invention to limit the voltage between line 22 and ground, gap 24 is connected in parallel with coil 2|, from line 22 to plate Hi, to -by-pass such currents around the coil and avoid such a voltage drop.

Under normal conditions there is no current across the gap between electrodes I2 and i3 and the voltage acros thi gap is that from line 22 to ground. There is no current through coil 2| or gap 24, and no voltage drop across them. If a dangerously high transient appears on line 22, it will rfirst break down the gap between electrodes I2 and I3 and establish a current from line 22 through coil 2|, then across the gap from electrode I3 to electrode .|'2 and to ground. If, asis-usually the case, the'transient includes component with rapid rates of change of current, gap 24 will then break down after which the current will ifiOW through gap 24 rather than through coil 2|. .After the transient has been dissipated, power current from line 22 may follow the same path. However, this power current which would not include components with rapid rates of change would follow the path of lower impedance through coil 2| rather than flow through gap .24, and the arc across this gap would be rapidly extinguished. The magnetic field resulting from the current through coil 2| would react with the are between electrodes l2 and 3, :forcing the arc to move out into the arcing chamber as illustrated by the broken lines in Figure v2. This elongate the arc and forces it into a confined space increasing the arc drop to such an extent that the arc is extinguished. This act on of elongating the arc and forcing itinto a confined space to extinguish it is so rapid and effective that it has been found. for example, that a -(SO-cycle power fault current which otherwise would reach a magnitude of 900 amperes crest is snuffed out in 0.003 second, after reaching a crest magnitude of only 300 amperes. In the conventional lightning arrester applied to an alternating current circuit, the alternating power. voltage results in an alternating power follow current, and interruption of this current occurs at a time when the alternating current'wave is passing-through a zero point. Such .:a lightning arrester cannot function prop- .4 erly at its full rated voltage when applied to a direct current circuit, because the power follow current through the arrester is not alternating in nature and does not provide the favorable opportunity for current interruption at a current zero. In the present invention the current interrupting action is so effective that interruption is not dependent upon the alternating nature of the current wave. This i illustrated by the case cited above where the current was extinguished in 0.003 second, even though the normal duration to the first current zero of the alternating wave would have been 0.0083 second. Hence it will be obvious that the device can be applied to direct current circuits as well as alternating current circuits.

It will be a parent that the blocks l0 and II may be mainta ned together in a suitable manner and that the coil instead of enc rcling the body may be positioned at one end thereof and have an overall diameter approximately equal to the diameter of the bod However, the arrangement illustrated is preferred and facil tates the stacking of a number of such units within a weather resistant hous ng such as is shown in Patent 2.422.9 8 to Olsen granted June 24, 1947, and ass ned to the same assignee as the present app cation. Obviously, in such an arrangement there would be no necessity for a means to hold the blocks of each unit together s nce a biasing spring at one end of the stack would serve this function. It will furthermore be a parent that in lieu of a pair of blocks a sin le inte ral body of any shape or configuration may be employed in accordance with this invention solong as the walls of the arcin chamber therein progressively converge away from the vicin ty adjacent the gap spacing and eventually come together at points remote therefrom.

Therefore, while I have, in accordance with the patent statutes, shown a particular embodiment of my invention, other chan es or modifications will be obvious to those skilled in the art and I, therefore, aim in the appended claims to cover all such changes or modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit interrupter comprising a pair of abutting slabs of insulating material and a pair of spaced electrodes mounted between said slabs at the periphery thereof defining an arc gap, an enclosed arc chamber in communication with said gap and defined by the opposing surfaces of said slabs, said surfaces "having a maximum spacing adjacent said electrodes converging progressively together at points remote from said gap and a winding mounted adjacent said slabs and connected electrically in series with said gap, the field produced by said winding when energized being effective "to elongate and move an are established between said electrodes to the convergence of said surfaces for extinguishment thereof.

2. An electric circuit interrupter comprising'a pair of abutting slabs of insulating material defining an arc chamber therebetween, a pair of spaced electrodes defining an arc gap mounted between said slabs at the periphery thereof and of said chamber, said gap being in communication with said chamber, opposite walls of said chamber having a maximum spacing adjacent said electrodes progressively converging together at points remote from said gap and a winding mounted adjacent saidslabs and connected elec- 5 trically in series with said electrodes and the gap therebetween, the field produced by said winding when energized being effective to elongate and move an are established between said electrodes to the convergence of said walls for extinguishment thereof.

3. An electric circuit interrupter comprising a pair of abutting blocks of insulating material and a pair of spaced electrodes mounted between said blocks at the periphery thereof and defining an arc gap, the opposing face of at least one of said blocks being depressed inwardly from the abutting edge thereof to define an enclosed arc chamber, opposite walls of said chamber having a maximum wall spacing adjacent said electrodes progressively decreasing to zero spacing at poinm remote from said gap, said gap being in communication with said chamber, and a coil mounted adjacent said blocks and connected electrically in series with said electrodes and the gap therebetween, the field produced by said coil when energized being effective to elongate and move an are established between said electrodes to the intersection of said walls at said remote points for extinguishment thereof.

4. An electric circuit interrupter comprising a pair of abutting blocks of insulating material and a pair of spaced electrodes mounted between said blocks at the periphery thereof and defining an arc gap, the opposing faces of each of said blocks being depressed inwardly from the abutting edges thereof to define an enclosed arc chamber, opposite walls of said chamber having a maximum wall spacing adjacent said electrodes progressively decreasing to zero spacing at points remote from said gap, said gap being in communication with said chamber, and a winding mounted adjacent said blocks and connected electrically in series with said gap, the field produced by said winding when energized being effective to elongate and move an arc established between said electrodes to the intersection of said walls at said remote points for extinguishment thereof.

5. An electric circuit interrupter comprising a pair of identical abutting blocks of insulating material having a cylindrical external configuration and a pair of spaced electrodes defining an arc gap mounted between said blocks, a pair of circular disks of conducting material mounted respectively on the external end surfaces of said blocks, said electrodes respectively supported by said blocks at the periphery thereof and respectively connected electrically to said conducting disks, the opposing surfaces of said blocks being depressed gradually inwardly from the abutting edges thereof to define a substantially enclosed arcing chamber opposite walls of which have a maximum spacing adjacent said gap and converge together at slopes to define an acute angle therebetween and form an enclosed periphery at points remote from said electrodes and a coil winding mounted adjacent to and encircling said blocks, said winding being connected electrically in series with one of said conducting disks whereby an are established between said electrodes will be elongated and moved by the resulting field of said winding to the periphery of said chamber for extinguishment thereof.

6. An electric circuit interrupter comprising a body of insulating material having a hollow portion defining an arc chamber within said body, means positioned at the periphery of said body defining an arc gap at said periphery and in communication with said chamber, opposite walls of said chamber having a maximum spacing adjacent said gap defining means progressively converging together to zero spacing at points remote from said gap means and magnetic means mounted adjacent said body providing a magnetic field so that an are established across said are gap means will be elongated and moved by said field to the convergence of said walls for extinguishment thereof.

JOHN W. KALB.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,515,074 Schermerhorn Nov. 11, 1924 1,825,298 Baker Sept. 29, 1931 2,443,017 Arone et al June 8, 1948 OTHER REFERENCES Wade, abstract of application Serial No. 635,316, published Oct. 4, 1949, 627 O. G. 263. 

